This kind of fanfiction is not appropriate. Fanfiction should be a creative way to explore the relationships and stories within the framework of the original work in a positive and respectful way. An 'orgy' theme for these characters is not in line with the family - friendly and positive - value - centered nature of the 'Harry Potter' series, and it is also disrespectful to the fans who appreciate the original work.
It could be due to a time - travel related plot. Perhaps Hermione goes back in time and through some unforeseen circumstances, her family line gets intertwined with Sirius' family, making her his sister in an alternate timeline. This could involve her interfering with past events that change family structures.
Well, the original 'Harry Potter' story is about magic, friendship, and the battle against evil. 'Sirus and Hermione' have their own relationships and roles within that framework which are mainly platonic and story - driven. The 'orgy fanfiction' completely goes against the nature of these characters and the overall positive and family - friendly tone of the original work.
One plotline could be that Hermione starts working on a project related to wizarding laws and Percy Weasley is also involved. As they collaborate, they realize they have a lot more in common than they thought. Their relationship gradually develops as they debate and discuss different legal aspects, and Hermione finds Percy's new - found confidence after leaving the Ministry very attractive.
It's not common at all. Fanfiction is a creative outlet for fans to expand on the stories and characters they adore. While there are many different themes explored, including some dark ones, the idea of a girl ending up sold is rather extreme. Writers typically aim to create engaging and enjoyable stories that stay within the bounds of what the majority of the fan community would be interested in. This type of plot is more likely to be found in very niche or edgy corners of the fanfiction world, rather than being a widespread or commonly - seen type.
In the fanfiction, Hermione and her older sister could have a complex relationship. Maybe the sister is overprotective, constantly looking out for Hermione at Hogwarts, especially with all the dangerous situations she gets into. The sister could also be a bit jealous of Hermione's academic success and magical abilities, which could lead to some sibling rivalry.
In some fanfictions, it's possible for the author to create a fictional relationship where Hermione is Molly's sister. However, in the original 'Harry Potter' series, there is no such relation.
One possible fanfiction plot could be that with Hermione being Harry's sister, it adds a new layer of family drama to the relationship between Hermione and Draco. Maybe Draco has to face his own prejudices in a different way because she's not just a Muggle - born witch but also related to 'The Boy Who Lived'.
In some fanfiction, creative liberties are taken to create unexpected relationships. If Hermione is depicted as Lucifer's sister, it could be a very interesting take. It might be used to explore themes of good and evil in a new context, with Hermione's intelligence and moral compass clashing or interacting with Lucifer's more devilish nature. However, this is a far - fetched concept when considering the original Harry Potter and Lucifer - related canons which are from completely different fictional universes.